Aluminum alloy material, and conductive member, battery member, fastening component, spring component, and structural component including the aluminum alloy material

ABSTRACT

An aluminum alloy material has an alloy composition consisting of 0.2 to 1.8% by mass of Mg, 0.2 to 2.0% by mass of Si, 0.01 to 1.50% by mass of Fe, with the balance containing Al and inevitable impurities. The aluminum alloy material has a fibriform metallographic structure where crystal grains extend so as to be aligned in one direction. In a cross section parallel to the one direction, an average value of a size perpendicular to a longitudinal direction of the crystal grains is 270 nm or less.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of International Patent ApplicationNo. PCT/JP2017/025211 filed Jul. 11, 2017, which claims the benefit ofJapanese Patent Application No. 2016-138841 filed Jul. 13, 2016, thefull contents of all of which are hereby incorporated by reference intheir entirety.

BACKGROUND Technical Field

The present disclosure relates to an aluminum alloy material having ahigh strength. Such an aluminum alloy material is used for a wide rangeof applications (for example, a conductive member, a battery member, afastening component, a spring component, and a structural component).

Description of the Related Art

In recent years, with the diversification of the shapes of metalmembers, a technique is being widely studied which causes a metal powderto be sintered using electron beams or lasers or the like, therebymolding a three-dimensional structure having a desired shape. However,such a technique uses the metal powder, and has for example thefollowing problem: an excessively fine metal powder is apt to explode.

Therefore, these days, a technique is being developed which molds athree-dimensional structure according to a method for knitting, weaving,tying, jointing, or connecting metal fine wires. The consideration ofsuch a method is advanced, for example, as Wire-Woven CellularMaterials, and the application of the method to a battery component, aheat sink, and an impact absorption member or the like is expected.

An iron-based or copper-based wire rod has been widely used as the metalfine wire. These days, there is considered substitution of theiron-based or copper-based metal material to an aluminum-based materialhaving a small specific gravity, a large thermal expansion coefficient,comparatively good electrical and heat conductivities, and excellentcorrosion resistance, particularly having a small elastic coefficient,and flexibly elastically deformed as compared with the iron-based orcopper-based metal material.

However, a pure aluminum material has the following problem: it has alower strength than that of the iron-based or copper-based metalmaterial. A 2000 or 7000-series aluminum alloy material which is analuminum-based alloy material having a comparatively high strength hasthe following problem: it has poor corrosion resistance and stresscorrosion cracking resistance.

Therefore, these days, there is widely used a 6000-series aluminum alloymaterial which contains Mg and Si and has excellent electrical and heatconductivities, and excellent corrosion resistance. Such a 6000-seriesaluminum alloy material has a higher strength in aluminum-based alloymaterials, but it does not have a sufficient strength, whereby a furtherimprovement in a strength is desired.

On the other hand, a method according to crystallization of an aluminumalloy material containing an amorphous phase (Japanese PatentApplication Publication No. 5-331585), a method for forming fine crystalgrains according to the ECAP method (Japanese Patent ApplicationPublication No. 9-137244), a method for forming fine crystal grainsaccording to cold working at a temperature equal to or less than roomtemperature (Japanese Patent Application Publication No. 2001-131721),and a method for dispersing carbon nanofibers (Japanese PatentApplication Publication No. 2010-159445) or the like are known as amethod for improving the strength of the aluminum alloy material.However, the methods manufacture aluminum alloy materials having smallsizes, which make it difficult to industrially put the aluminum alloymaterials to practical use.

A method for controlling a rolling temperature to obtain an Al—Mg-basedalloy having a fine structure is disclosed in Japanese PatentApplication Publication No. 2003-027172. The method has excellentindustrial mass productivity, but a further improvement in a strength isrequired.

SUMMARY

The present disclosure is related to providing an aluminum alloymaterial which can serve as a substitute for an iron-based orcopper-based metal material and has a high strength, and providing aconductive member, a battery member, a fastening component, a springcomponent, and a structural component including the aluminum alloymaterial.

According to a first aspect of the present disclosure, an aluminum alloymaterial has an alloy composition consisting of 0.2 to 1.8% by mass ofMg, 0.2 to 2.0% by mass of Si, 0.01 to 1.50% by mass of Fe, with thebalance containing Al and inevitable impurities. The aluminum alloymaterial has a fibriform metallographic structure where crystal grainsextend so as to be aligned in one direction. In a cross section parallelto the one direction, an average value of a size perpendicular to alongitudinal direction of the crystal grains is 270 nm or less.

Further, it is preferable that an aspect ratio of the crystal grains isin excess of 10.

Further, it is preferable that the aluminum alloy material has a Vickershardness (HV) of 125 to 250.

According to a second aspect of the present disclosure, aconductivemember includes the aluminum alloy material according to the presentdisclosure.

According to a third aspect of the present disclosure, a battery memberincludes the aluminum alloy material according to the presentdisclosure.

According to a fourth aspect of the present disclosure, a fasteningcomponent includes the aluminum alloy material according to the presentdisclosure.

According to a fifth aspect of the present disclosure, a springcomponent includes the aluminum alloy material according to the presentdisclosure.

According to a sixth aspect of the present disclosure, a structuralcomponent includes the aluminum alloy material according to the presentdisclosure.

The present disclosure can provide an aluminum alloy material having ahigh strength comparable to that of an iron-based or copper-based metalmaterial. Furthermore, the present disclosure can provide a conductivemember, a battery member, a fastening component, a spring component, anda structural component including the aluminum alloy material.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A perspective view schematically showing the situation of themetallographic structure of an aluminum alloy material according to thepresent disclosure.

FIG. 2 A graph showing the relationship between the degree of workingand tensile strength of each of pure aluminum, pure copper, and analuminum alloy material according to the present disclosure.

FIG. 3 A STEM image showing the situation of a metallographic structurein a cross section parallel to a working direction X of an aluminumalloy material according to the Examples.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of an aluminum alloy material of thepresent disclosure are described in detail. The aluminum alloy materialaccording to the present disclosure has an alloy composition consistingof 0.2 to 1.8% by mass of Mg, 0.2 to 2.0% by mass of Si, 0.01 to 1.50%by mass of Fe, with the balance containing Al and inevitable impurities.The aluminum alloy material has a fibriform metallographic structurewhere crystal grains extend so as to be aligned in one direction. In across section parallel to the one direction, the average value of a sizeperpendicular to the longitudinal direction of the crystal grains is 270nm or less.

Herein, the “crystal grains” refer to portions surrounded by orientationdifference boundaries. Here, the “orientation difference boundary”refers to a boundary where contrast discontinuously changes in a case inwhich a metallographic structure is observed by scanning transmissionelectron microscopy (STEM). The size perpendicular to the longitudinaldirection of the crystal grains corresponds to the interval of theorientation difference boundaries.

The aluminum alloy material according to the present disclosure has afibriform metallographic structure where crystal grains extend so as tobe aligned in one direction. Here, FIG. 1 shows a perspective viewschematically showing the situation of the metallographic structure ofthe aluminum alloy material according to the present disclosure. Asshown in FIG. 1, the aluminum alloy material of the present disclosurehas a fibriform structure where crystal grains 10 each having anelongated shape extend so as to be aligned in one direction X. Thecrystal grains each having an elongated shape are completely differentfrom conventional fine crystal grains and flat crystal grains eachmerely having a large aspect ratio. Specifically, the crystal grains ofthe present disclosure each have an elongated shape as with a fiber, andthe average value of a size t perpendicular to a longitudinal directionX thereof is 270 nm or less. The fibriform metallographic structurewhere the fine crystal grains extend so as to be aligned in onedirection can be said to be a novel metallographic structure which isnot included in a conventional aluminum alloy.

The aluminum alloy material of the present disclosure has the fibriformmetallographic structure where the crystal grains extend so as to bealigned in one direction, and in the cross section parallel to the onedirection, the average value of the size perpendicular to thelongitudinal direction of the crystal grains is controlled to 270 nm orless, whereby a high strength (for example, a tensile strength of 480MPa or more and a Vickers hardness (HV) of 125 or more) comparable tothat of an iron-based or copper-based metal material can be attained.

The fine crystal grain size leads directly to an effect of improvinggrain boundary corrosion, an effect of improving fatiguecharacteristics, an effect of reducing the roughness of a surface afterplastic working, and an effect of reducing sagging and burr duringshearing working, or the like in addition to an improvement in astrength, which provides effects of generally improving the functions ofthe material.

Such an aluminum alloy material of the present disclosure can attain ahigh strength even in an Al—Mg—Si—Fe-based alloy material having analloy composition containing less constituent elements, and the lessconstituent elements can also largely improve recyclability.

(1) Alloy Composition

The alloy composition of the aluminum alloy material of the presentdisclosure and the effects of the alloy composition are described.

<Mg: 0.2 to 1.8% by mass>

Mg (magnesium) has an effect of strengthening by forming a solidsolution in an aluminum matrix, and has an effect of improving a tensilestrength by a synergistic effect with Si. In a case where it forms aMg—Si cluster as a solute atom cluster, it is an element having aneffect of improving a tensile strength and an elongation. However, in acase where a Mg content is less than 0.2% by mass, the above functioneffects are insufficient. In a case where the Mg content is in excess of1.8% by mass, a crystallized material is formed, which causesdeterioration in workability (wire drawing workability and bendingworkability or the like). Therefore, the Mg content is 0.2 to 1.8% bymass, and preferably 0.4 to 1.0% by mass.

<Si: 0.2 to 2.0% by Mass>

Si (silicon) has an effect of strengthening by forming a solid solutionin an aluminum matrix, and has an effect of improving a tensile strengthand bending fatigue resistance by a synergistic effect with Mg. In acase where it forms a Mg—Si cluster or an Si—Si cluster as a solute atomcluster, it is an element having an effect of improving a tensilestrength and an elongation. However, in a case where a Si content isless than 0.2% by mass, the above function effects are insufficient. Ina case where the Si content is in excess of 2.0% by mass, a crystallizedmaterial is formed, which causes deterioration in workability.Therefore, the Si content is 0.2 to 2.0% by mass, and preferably 0.4 to1.0% by mass.

<Fe: 0.01 to 1.50% by mass>

Fe (iron) is an element which contributes to refinement of crystalgrains by forming an Al—Fe based intermetallic compound and provides animproved tensile strength. Here, the intermetallic compound refers to acompound composed of two or more kinds of metals. Fe dissolves in Alonly by 0.05% by mass at 655° C., and even less at room temperature.Accordingly, the remaining Fe which cannot dissolve in Al iscrystallized or precipitated as an intermetallic compound such as Al—Fe,Al—Fe—Si, or Al—Fe—Si—Mg. An intermetallic compound mainly composed ofFe and Al as exemplified by the above-described intermetallic compoundsis herein referred to as a Fe-based compound. This intermetalliccompound contributes to the refinement of crystal grains and provides animproved tensile strength. Fe has, also by Fe which has dissolved in Al,an effect of providing an improved tensile strength. In a case where aFe content is less than 0.01% by mass, these function effects areinsufficient. In a case where the Fe content is in excess of 1.50% bymass, a crystallized material increases, which causes deterioration inworkability. Here, the crystallized material refers to an intermetalliccompound occurring during the casting solidification of an alloy.Therefore, the Fe content is 0.01 to 1.50% by mass, and preferably 0.05to 0.80% by mass. In a case where a cooling speed during casting isslow, the dispersion of the Fe-based compound is sparse, which causesthe increased degree of a negative effect. Therefore, the Fe content ismore preferably less than 1.00% by mass, and still more preferably lessthan 0.60% by mass.

<Balance: Al and Inevitable Impurities>

The balance, i.e., components other than those described above, includesAl (aluminum) and inevitable impurities. Herein, the inevitableimpurities mean impurities contained by an amount which may be containedinevitably during a manufacturing process. Since the inevitableimpurities may cause a decrease in conductivity depending on the contentthereof, it is preferable to suppress the content of the inevitableimpurities to some extent considering the decrease in the conductivity.Examples of components which are inevitable impurities include B(boron), Ti (titanium), Cr (chromium), Mn (manganese), Cu (copper), Ni(nickel), Zn (zinc), Zr (zirconium), Bi (bismuth), Pb (lead), Ga(gallium), Sn (tin), and Sr (strontium). The upper limit of the contentof each of the components may be 0.05% by mass or less, and the totalamount of the components may be 0.15% by mass or less.

Such an aluminum alloy material can be obtained by combining andcontrolling alloy compositions and manufacturing processes. Hereinafter,a suitable manufacturing method of the aluminum alloy material of thepresent disclosure is described.

(2) Manufacturing Method of Aluminum Alloy Material According to OneExample of Present Disclosure

Such an aluminum alloy material according to one example of the presentdisclosure particularly attains an improvement in a strength byintroducing a crystal grain boundary into an Al—Mg—Si—Fe-based alloy ata high density. Therefore, an approach to an improvement in a strengthis largely different from that in a method for precipitation-hardening aMg—Si compound which has been generally performed in a conventionalaluminum alloy material.

In a preferable manufacturing method of the aluminum alloy material ofthe present disclosure, an aluminum alloy material having apredetermined alloy composition is subjected to cold working [1] at adegree of working of 4 or more as last working without subjecting thealuminum alloy material to an aging precipitation heat treatment [0].Refine annealing [2] may be performed after the cold working [1] ifneeded. Hereinafter, the manufacturing method is described in detail.

Usually, in a case in which deformation stress is applied to a metalmaterial, crystal slip occurs as the elementary step of the deformationof a metal crystal. The metal material in which the crystal slip is aptto occur has small stress required for deformation, whereby it can besaid to be have a low strength. Therefore, it is important to suppressthe crystal slip which occurs in the metallographic structure in orderto provide the improvement in the strength of the metal material.Examples of the prevention factor of such crystal slip include theexistence of the crystal grain boundary in the metallographic structure.Such a crystal grain boundary can prevent the crystal slip fromspreading in the metallographic structure in a case in which thedeformation stress is applied to the metal material. As a result, thestrength of the metal material is improved.

Therefore, it is considered that, in order to improve the strength ofthe metal material, the crystal grain boundary is desirably introducedat a high density into the metallographic structure. Here, the formationmechanism of the crystal grain boundary is considered to be the divisionof the metal crystal involving the following deformation of themetallographic structure, for example. Usually, in a polycrystallinematerial, the difference between the orientations of adjacent crystalgrains, and the space distribution of distortion between the vicinity ofa surface layer brought into contact with a working tool and the insideof bulk cause a stress state to be in a complicated multiaxial state.Under these influences, a crystal grain which is in a single orientationbefore deformation is divided in a plurality of orientations with thedeformation, and a crystal grain boundary is formed between the dividedcrystals.

However, the formed crystal grain boundary has surface energy in astructure deviated from the closest packed atomic arrangement of usualtwelve coordination. Therefore, it is considered that, in the usualmetallographic structure, in a case in which the crystal grain boundaryhas a given density or more, the increased internal energy serves as adriving force, whereby dynamic or static recovery and recrystallizationoccur. Therefore, usually, it is considered that the increase andreduction of the crystal grain boundary simultaneously occur even if theamount of deformation is increased, whereby a grain boundary density issaturated.

Such a phenomenon coincides with also the relationship between a degreeof working and a tensile strength in pure aluminum or pure copper whichis a conventional metallographic structure. FIG. 2 shows a graph of therelationship between the degree of working and tensile strength of eachof pure aluminum, pure copper, and the aluminum alloy material accordingto the present disclosure.

As shown in FIG. 2, pure aluminum or pure copper which is a usualmetallographic structure has an improved tensile strength (hardening) ata comparatively low degree of working, but as the degree of workingincreases, the amount of hardening tends to be saturated. Here, it isconsidered that the degree of working corresponds to the amount ofdeformation applied to the metallographic structure, and the saturationof the amount of hardening corresponds to the saturation of the grainboundary density.

On the other hand, it was found that the aluminum alloy material of thepresent disclosure is continuously hardened even if the degree ofworking increases, and the strength of the aluminum alloy materialcontinuously increases with working. This is considered to be becausethe aluminum alloy material of the present disclosure has the abovealloy composition, and particularly, predetermined amounts of Mg and Siare compositely added to the aluminum alloy material, whereby theincrease in the internal energy can be suppressed even if the crystalgrain boundary has a given density or more in the metallographicstructure. This is considered to make it possible to prevent recoveryand recrystallization in the metallographic structure, and effectivelyincrease the crystal grain boundary in the metallographic structure.

The mechanism of the improvement in the strength provided by thecomposite addition of Mg and Si is not necessarily clear. However, themechanism is considered to be based on the following (i) and (ii): (i)by combining and using a Mg atom having a greater atomic radius thanthat of an Al atom and an Si atom having a smaller atomic radius thanthat of the Al atom, the atoms are always filled densely (arranged) inthe aluminum alloy material; and (ii) by causing divalent Mg andtetravalent Si to coexist with respect to a trivalent Al atom, atrivalent state can be formed in the entire aluminum alloy material,which attains valence stability, whereby the increase in the internalenergy involving working can be effectively suppressed.

In the present disclosure, the degree of working in the cold working [1]is set to 4 or more. In particular, working at a large degree of workingmakes it possible to prompt the division of the metal crystal involvingthe deformation of the metallographic structure, and to introduce thecrystal grain boundary into the aluminum alloy material at a highdensity. As a result, the grain boundary of the aluminum alloy materialis strengthened to largely improve the strength. Such a degree ofworking is set to preferably 5 or more, more preferably 6 or more, andstill more preferably 7 or more. The upper limit of the degree ofworking is not particularly prescribed, and usually 15 or less.

A degree of working η is represented by the following formula (1) in acase in which a cross-sectional area before working is taken as s1, anda cross-sectional area after working is taken as s2 (s1>s2).

Degree of working (non-dimension): η=ln(s1/s2)  (1)

A working rate is preferably set to 98.2% or more, and more preferably99.8% or more. A working rate R is represented by the following formula(2) using the above s1 and s2.

Working rate (%): R={(s1−s2)/s1}×100  (2)

A working method may be appropriately selected according to the intendedshape (a wire bar, a plate, a strip, a foil or the like) of the aluminumalloy material, and examples thereof include a cassette roller die,groove roll rolling, round wire rolling, drawing working using a die orthe like, and swaging. Various conditions (kind of lubricating oil,working speed, and working heat generation or the like) in the aboveworking may be appropriately adjusted in a known range.

The aluminum alloy material is not particularly limited as long as ithas the above alloy composition. For example, it is possible toappropriately select and use an extruded material, an ingot material, ahot-rolled material, and a cold-rolled material or the like according tothe purpose of use.

In the present disclosure, the aging precipitation heat treatment [0]which has been conventionally performed before the cold working [1] isnot performed. Such an aging precipitation heat treatment [0] usuallyretains the aluminum alloy material at 160 to 240° C. for 1 minute to 20hours, to prompt precipitation of a Mg—Si compound. However, in a casein which the aluminum alloy material is subjected to such an agingprecipitation heat treatment [0], the above cold working [1] at the highdegree of working cannot be performed since working cracks occur in thematerial. Since a high aging temperature causes an overaging state, theworking cracks may not occur even in the above cold working [1] at thehigh degree of working. However, in this case, Mg and Si are dischargedfrom an Al matrix phase as a Mg—Si compound, whereby the stability ofthe grain boundary remarkably deteriorates.

In the present disclosure, the refine annealing [2] may be performedafter the cold working [1] for the purposes of release of residualstress and an improvement in an elongation. In a case in which therefine annealing [2] is performed, a treatment temperature is set to 50to 160° C. In a case in which the treatment temperature of the refineannealing [2] is less than 50° C., the above effects are less likelyobtained. In a case in which the treatment temperature is in excess of160° C., recovery or recrystallization causes the growth of the crystalgrains to occur, which causes a decrease in the strength. The retentiontime of the refine annealing [2] is preferably 1 to 48 hours. Thevarious conditions of such a heat treatment can be appropriatelyadjusted according to the kind and amount of inevitable impurities, andthe solid solution/precipitation state of the aluminum alloy material.

In the present disclosure, as described above, the aluminum alloymaterial is subjected to working at a high degree of working accordingto a method such as drawing using a die, or rolling. Therefore, as aresult, an elongated aluminum alloy material is obtained. On the otherhand, a conventional method for manufacturing an aluminum alloy materialsuch as powder sintering, compression torsion working, high pressuretorsion (HPT), forge working, or equal channel angular pressing (ECAP)makes it difficult to provide the elongated aluminum alloy material. Thealuminum alloy material of the present disclosure is preferablymanufactured so as to have a length of 10 m or more. The upper limit ofthe length of the aluminum alloy material during manufacturing is notparticularly provided, and preferably 6000 m or less in consideration ofworkability or the like.

Since it is effective to increase the degree of working for providingfine crystal grains as described above, the configuration of the presentdisclosure is likely to be attained as the diameter of the aluminumalloy material of the present disclosure is smaller, particularly, in acase in which the aluminum alloy material is produced as a wire bar, oras the thickness of the aluminum alloy material is smaller in a case inwhich the aluminum alloy material is produced as a plate or a foil.

In particular, in a case in which the aluminum alloy material of thepresent disclosure is a wire bar, the wire bar has a wire diameter ofpreferably 1 mm or less, more preferably 0.5 mm or less, still morepreferably 0.1 mm or less, and particularly preferably 0.07 mm or less.The upper limit is not particularly provided, and preferably 30 mm orless. The aluminum alloy wire bar of the present disclosure has oneadvantage that it can be used as a thin single wire.

As described above, the aluminum alloy material of the presentdisclosure is slimly or thinly worked. A plurality of aluminum alloymaterials are prepared and joined to provide a large or thick product,which can also be used for the intended application. A known method canbe used for the joining method, and examples thereof include pressurewelding, welding, joining using an adhesive, and friction stirringjoining. In a case in which the aluminum alloy material is the wire bar,a plurality of wire bars are bundled, and twisted to provide a twistedproduct, which can also be used for the intended application as analuminum alloy twisted wire. The aluminum alloy material subjected tothe cold working [1] may be subjected to working according to joining ortwisting, and then subjected to the step of the refine annealing [2].

(3) Organizational Feature of Aluminum Alloy Material of PresentDisclosure

The aluminum alloy material of the present disclosure manufactured bythe above manufacturing method is obtained by introducing the crystalgrain boundary at a high density into the metallographic structure. Thealuminum alloy material of the present disclosure has the fibriformmetallographic structure where the crystal grains extend so as to bealigned in one direction, and in the cross section parallel to the onedirection, the average value of a size perpendicular to the longitudinaldirection of the crystal grains is 270 nm or less. The aluminum alloymaterial has a non-conventional specific metallographic structure,whereby the aluminum alloy material can exhibit a particularly excellentstrength.

The metallographic structure of the aluminum alloy material of thepresent disclosure is the fibriform structure, and the crystal grainseach having an elongated shape extend in fiber forms so as to be alignedin one direction. Here, the “one direction” corresponds to the workingdirection of the aluminum alloy material. In a case in which thealuminum alloy material is the wire bar, the “one direction” correspondsto a wire drawing direction, for example. In a case in which thealuminum alloy material is a plate or a foil, the “one direction”corresponds to a rolling direction, for example. Particularly, thealuminum alloy material of the present disclosure exhibits aparticularly excellent strength with respect to tensile stress parallelto the working direction.

The one direction preferably corresponds to the longitudinal directionof the aluminum alloy material. Specifically, as long as the aluminumalloy material is not divided into pieces so as to have a size shorterthan a size perpendicular to the working direction, the workingdirection of the aluminum alloy material usually corresponds to thelongitudinal direction.

In the cross section parallel to the one direction, the average value ofa size perpendicular to the longitudinal direction of the crystal grainsis 270 nm or less, more preferably 220 nm or less, still more preferably170 nm or less, and particularly preferably 120 nm or less. In thefibriform metallographic structure where the crystal grains having asmall diameter (size perpendicular to the longitudinal direction of thecrystal grains) extend in one direction, the crystal grain boundary isformed at a high density. Such a metallographic structure makes itpossible to effectively inhibit the crystal slip involving deformation,which makes it possible to attain a non-conventional high strength. Thelower limit of the average value of a size perpendicular to thelongitudinal direction of the crystal grains is preferably 50 nm or morefrom the viewpoint of preventing deterioration in ductility.

The size of the longitudinal direction of the crystal grains is notnecessarily specified, and preferably 1200 nm or more, more preferably1700 nm or more, and still more preferably 2200 nm or more. The aspectratio of the crystal grains is preferably in excess of 10, and morepreferably 20 or more. The upper limit of the aspect ratio of thecrystal grains is preferably 2 million or less from the viewpoint ofpreventing deterioration in ductility.

(4) Characteristics of Aluminum Alloy Material of Present Disclosure[Tensile Strength]

A tensile strength is measured according to JIS Z2241: 2011. Detailedmeasurement conditions are described in the column of Examples to bedescribed below. In a case in which the aluminum alloy material of thepresent disclosure is particularly the wire bar, the aluminum alloymaterial has a tensile strength of preferably 480 MPa or more. This is astrength equivalent to that of a copper wire subjected to wire drawingworking at a general high degree of working. The aluminum alloy materialhas a tensile strength of more preferably 520 MPa or more, still morepreferably 560 MPa or more, particularly preferably 600 MPa or more, andyet still more preferably 640 MPa or more. The aluminum alloy materialof the present disclosure having such a high strength can be used assubstitution of a strong wire drawing worked material made of a thincopper alloy such as a Cu—Sn and Cu—Cr alloy. Such an aluminum alloymaterial can also be used as substitution of a steel-based orstainless-based material. The upper limit of the tensile strength of thealuminum alloy material of the present disclosure is not particularlylimited, and 1000 MPa or less, for example.

[Vickers Hardness (HV)]

A Vickers hardness (HV) is a value measured according to JIS Z 2244:2009. Detailed measurement conditions are described in the column ofExamples to be described below. The Vickers hardness (HV) of a workedproduct which has been already turned into a component can be measuredas follows: the worked product is disassembled; the cross sectionthereof is subjected to mirror polishing; and the Vickers hardness ofthe cross section is measured. In a case in which the aluminum alloymaterial of the present disclosure is particularly the wire bar, theVickers hardness (HV) is preferably 125 or more. This is a strengthequivalent to that of a copper wire subjected to general strong wiredrawing working. The Vickers hardness (HV) of the aluminum alloymaterial is more preferably 140 or more, still more preferably 150 ormore, particularly preferably 160 or more, and yet still more preferably170 or more. The aluminum alloy material of the present disclosurehaving such a high strength can be used as substitution of a strong wiredrawing worked material made of a thin copper alloy such as a Cu—Sn orCu—Cr alloy. Such an aluminum alloy material can also be used assubstitution of a steel-based or stainless-based material. The upperlimit of the Vickers hardness (HV) of the aluminum alloy material of thepresent disclosure is not particularly limited, and 300 or less, forexample, and preferably 250 or less.

(5) Application of Aluminum Alloy Material of Present Disclosure

The aluminum alloy material of the present disclosure can be directed toall the applications in which an iron-based material, a copper-basedmaterial, and an aluminum-based material are used. Specifically, thealuminum alloy material can be suitably used as a conductive member suchas an electric wire or a cable, a battery member such as a currentcollector mesh or net, a fastening component such as a screw, a bolt, ora rivet, a spring component such as a coil spring, an electric contactspring member such as a connector or a terminal, a structural componentsuch as a shaft or a frame, a guide wire, a semiconductor bonding wire,and a winding wire used for a dynamo or a motor, or the like.

More specific application examples of the conductive member include apower electric wire such as an overhead power line, OPGW, a subterraneanelectric wire, or a submarine cable, a communication electric wire suchas a telephone cable or a coaxial cable, an appliance electric wire suchas a wired drone cable, a cab tire cable, an EV/HEV charge cable, atwisted cable for wind power on the ocean, an elevator cable, anumbilical cable, a robot cable, a train overhead wire, or a trolleywire, a transportation electric wire such as an automobile wire harness,a vessel electric wire, and an airplane electric wire, a bus bar, a leadframe, a flexible flat cable, a lightning rod, an antenna, a connector,a terminal, and a cable braid.

Examples of the battery member include a solar cell electrode.

More specific application examples of the structural component include ascaffold in a construction site, a conveyor mesh belt, a clothing metalfiber, a chain armor, a fence, an insect repellent net, a zipper, afastener, a clip, aluminum wool, a bicycle component such as a brakewire or a spoke, a reinforcement wire made of tempered glass, a pipeseal, a metal packing, a protection reinforcing material for a cable, afan belt cored bar, a wire for driving an actuator, a chain, a hanger, asound isolation mesh, and a shelf board.

More specific application examples of the fastening component include aset screw, a staple, and a drawing pin.

More specific application examples of the spring component include aspring electrode, a terminal, a connector, a semiconductor probe spring,a blade spring, and a flat spiral spring.

The aluminum alloy material is suitable also as a metal fiber to beadded in order to apply conductivity to a resin-based material, aplastic material, and a cloth or the like, and to control the strengthand elastic modulus thereof.

The aluminum alloy material is suitable also as a consumer member and amedical member such as an eyeglass frame, a clock belt, a nib of afountain pen, a fork, a helmet, or an injection needle.

In addition, the aluminum alloy having a high strength of the presentdisclosure is particularly suitably used as a metal conductorconstituting a health care wearable device requiring high elasticity. Ahigh material strength not easily causing plastic deformation, and goodfatigue characteristics causing no fracture even under repeateddeformation are required for the metal conductor. In particular, in acase in which the conductor unites the function of an electrode directlystuck on a human body, an aluminum alloy is preferably used as comparedwith a metal which is apt to cause allergy such as copper. Copper reactswith sweat or the like emitted from the human body, whichdisadvantageously causes occurrence of discoloration or rust. However,the aluminum alloy is advantageously less likely to cause such aproblem.

Hereinbefore, embodiments of the present disclosure have been described.However, the present disclosure is not limited to the above embodiments,and includes all aspects included in the concept of the presentdisclosure and appended claims, and various modifications can be madewithin the scope of the present disclosure.

EXAMPLES

Next, Examples and Comparative Examples are described to further clarifythe effects of the present disclosure. However, the present disclosureis not limited to these Examples.

Examples 1 to 13

First, bars having alloy compositions shown in Table 1 and each having adiameter of 10 mm were prepared. Next, aluminum alloy wire rods(diameter: 0.07 to 2.0 mm) were produced under manufacturing conditionsshown in Table 1 using the bars.

Comparative Example 1

In Comparative Example 1, an aluminum wire rod (diameter: 0.24 mm) wasproduced under a manufacturing condition shown in Table 1 using a barmade of 99.99% by mass of Al and having a diameter of 10 mm.

Comparative Examples 2 to 7

In Comparative Examples 2 to 7, aluminum alloy wire rods (diameter: 0.07to 2.0 mm) were produced under manufacturing conditions shown in Table 1using bars having alloy compositions shown in Table 1 and each having adiameter of 10 mm.

Manufacturing conditions A to K shown in Table 1 are specifically asfollows.

<Manufacturing Condition A>

The prepared bar was subjected to cold working [1] at a degree ofworking of 5.5. The bar was not subjected to refine annealing [2].

<Manufacturing Condition B>

The bar was subjected to cold working [1] under the same condition asthe manufacturing condition A except that the degree of working of thecold working [1] was set to 6.5.

<Manufacturing Condition C>

The bar was subjected to cold working [1] under the same condition asthe manufacturing condition A except that the degree of working of thecold working [1] was set to 7.5.

<Manufacturing Condition D>

The bar was subjected to cold working [1] under the same condition asthe manufacturing condition A except that the degree of working of thecold working [1] was set to 10.0.

<Manufacturing Condition E>

The prepared bar was subjected to cold working [1] at a degree ofworking of 4.5, and then subjected to refine annealing [2] at atreatment temperature of 60° C. for a retention time of 1 hour.

<Manufacturing Condition F>

The bar was subjected to cold working [1] and refine annealing [2] underthe same condition as the manufacturing condition E except that thedegree of working of the cold working [1] was set to 5.5.

<Manufacturing Condition G>

The bar was subjected to cold working [1] and refine annealing [2] underthe same condition as the manufacturing condition E except that thedegree of working of the cold working [1] was set to 6.5.

<Manufacturing Condition H>

The bar was subjected to cold working [1] and refine annealing [2] underthe same condition as the manufacturing condition E except that thedegree of working of the cold working [1] was set to 10.0.

<Manufacturing Condition I>

The bar was subjected to cold working [1] under the same condition asthe manufacturing condition A except that the degree of working of thecold working [1] was set to 3.5.

<Manufacturing Condition J>

The prepared bar was subjected to an aging precipitation heat treatment[0] at a treatment temperature of 180° C. for a retention time of 10hours, and then subjected to cold working [1]. However, since breakingof wire occurred frequently, the work was stopped.

<Manufacturing Condition K>

The prepared bar was subjected to cold working [1]. However, sincebreaking of wire occurred frequently, the work was stopped.

(Comparative Example 8): Manufacturing Condition P of Table 1

A virgin Al ingot for electrical purposes (JIS H 2110), an Al—Mg masteralloy, and an Al—Si master alloy were dissolved, to manufacture a moltenmetal having an alloy composition of Al-0.7% by mass Mg-0.7% by mass Si.This was cast, and a billet having a diameter of 60 mm and a length of240 mm was subjected to hot extruding at 470° C., to obtain a drawingstock. The obtained drawing stock was subjected to first wire drawingworking at a working rate of 70% (degree of working: 1.20), a primaryheat treatment at 130° C. for 5 hours, second wire drawing working at aworking rate of 60% (degree of working: 0.92), and thereafter asecondary heat treatment at 160° C. for 4 hours, to obtain an aluminumalloy wire rod (diameter: 2 mm).

(Comparative Example 9): Manufacturing Condition Q of Table 1

From a molten metal having an alloy composition of Al-0.51% by massMg-0.58% by mass Si—0.79% by mass Fe, a bar having a diameter of 10 mmwas obtained by a Properzi type continuous casting rolling machine. Theobtained bar was peeled so as to have a diameter of 9.5 mm. The bar wassubjected to first wire drawing working at a degree of working of 2.5, aprimary heat treatment at 300 to 450° C. for 0.5 to 4 hours, second wiredrawing working at a degree of working of 4.3, a secondary heattreatment at 612° C. for 0.03 seconds in a continuous current heattreatment (corresponding to temper annealing [2]), and thereafter anaging heat treatment at 150° C. for 10 hours, to obtain an aluminumalloy wire rod (diameter: 0.31 mm).

(Comparative Example 10): Manufacturing Condition R of Table 1

Into a graphite crucible, aluminum having a purity of 99.95% by mass,magnesium having a purity of 99.95% by mass, silicon having a purity of99.99% by mass, and iron having a purity of 99.95% by mass were chargedin predetermined amounts, and stirred and melted at 720° C. byhigh-frequency induction heating, to manufacture a molten metal havingan alloy composition of Al-0.6% by mass Mg-0.3% by mass Si—0.05% by massFe. This was moved to a container provided with a graphite die, andsubjected to continuous casting at a casting speed of about 300 mm/minvia the water-cooled graphite die, to obtain a wire having a diameter of10 mm and a length of 100 mm. A cumulative equivalent strain of 4.0 wasintroduced by the ECAP method. A recrystallization temperature obtainedat this stage was 300° C. The wire was subjected to prior heating in aninactive gas atmosphere at 250° C. for 2 hours. Next, the wire wassubjected to a first wire drawing treatment at a working rate of 29%(degree of working: 0.34). A recrystallization temperature obtained atthis stage was 300° C. The wire was subjected to a primary heattreatment in an inactive gas atmosphere at 260° C. for 2 hours. Then,the wire was passed at a drawing speed of 500 mm/min in a water-cooledwire drawing die, to be subjected to a second wire drawing treatment ata degree of working of 9.3. A recrystallization temperature obtained atthis stage was 280° C. The wire was subjected to a secondary heattreatment in an inactive gas atmosphere at 220° C. for 1 hour, to obtainan aluminum alloy wire rod (diameter: 0.08 mm).

[Evaluation]

The aluminum alloy wire rods according to the Examples and theComparative Examples were subjected to evaluation of characteristics tobe shown below. The evaluation conditions of the characteristics are asfollows. The results are shown in Table 1.

[1] Alloy Composition

Measurement was performed by the emission spectrochemical analysismethod according to JIS H1305: 2005. The measurement was performed usingan emission spectrophotometer (manufactured by Hitachi High-Tech ScienceCorporation).

[2] Structure Observation

A metallographic structure was observed by scanning transmissionelectron microscopy (STEM) using a transmission electron microscopeJEM-3100FEF (manufactured by JEOL Co., Ltd.). An observation sample tobe used was cut at a cross section parallel to the longitudinaldirection (wire drawing direction X) of the wire rod by focused ion beam(FIB) so as to have a thickness of 100 nm±20 nm, and finished by ionmilling. In the STEM observation, a boundary in which contrasts werediscontinuously different was recognized as a crystal grain boundarywith the difference between contrasts as the orientation of a crystalusing gray contrast. There may be no difference between gray contrastseven if crystal orientations are different depending on the diffractioncondition of an electron beam. In that case, while an angle between theelectron beam and the sample was changed by inclining by ±3 degrees bytwo sample rotational axes orthogonal to each other in a sample stage ofan electron microscope, the observed surface was photographed under aplurality of diffraction conditions, to recognize the grain boundary.The observed field of view was set to (15 to 40) μm×(15 to 40) μm, and acenter and a position near the middle of a surface layer (center sideposition separated by about ¼ of a wire diameter from the surface layerside) on a line corresponding to a wire diameter direction (directionperpendicular to a longitudinal direction) in the cross section wereobserved. The observed field of view was appropriately adjustedaccording to the size of a crystal grain. In the cross section parallelto the longitudinal direction (wire drawing direction X) of the wirerod, the presence or absence of the fibriform metallographic structurewas determined from an image photographed during the STEM observation.FIG. 3 shows a part of the STEM image of the cross section parallel tothe longitudinal direction (wire drawing direction X) of the wire rod ofExample 4 photographed during the STEM observation. In the presentExamples, the fibriform metallographic structure was estimated as“presence” in a case in which the metallographic structure as shown inFIG. 3 was observed. Furthermore, in each observed field of view,optional 100 crystal grains were selected. The size perpendicular to thelongitudinal direction of each crystal grain and the size parallel tothe longitudinal direction of the crystal grain were measured, tocalculate the aspect ratio of the crystal grain. Furthermore, theaverage values of the size perpendicular to the longitudinal directionof the crystal grains and the aspect ratios were calculated from thetotal of the observed crystal grains. In a case in which the observedcrystal grains were clearly larger than 400 nm, the number of selectionof the crystal grains whose size was measured was reduced, and theaverage value thereof was calculated. In a case in which the sizeparallel to the longitudinal direction of the crystal grains was clearly10 or more times the size perpendicular to the longitudinal direction ofthe crystal grains, the crystal grains were determined to uniformly havean aspect ratio of 10 or more.

[3] Tensile Strength

According to JIS Z2241: 2001, a tensile test was performed using aprecision universal tester (manufactured by Shimadzu Corporation), tomeasure a tensile strength (MPa). The test was carried out underconditions of a distance between marks of 10 cm and a deformation speedof 10 mm/min. Three of the wire rods were subjected to the tensile test,and the average values (N=3) thereof were defined as the tensilestrength of the wire rod. The tensile strength was preferably larger,and the tensile strength of 480 MPa or more was considered to be at apass level in the present Examples.

[4] Vickers Hardness (HV)

According to JIS Z 2244: 2009, a Vickers hardness (HV) was measuredusing a microhardness tester HM-125 (manufactured by Akashi Corporation(current Mitutoyo Corporation)). At this time, a test force was set to0.1 kgf, and a retention time was set to 15 seconds. Measurementpositions were a center and a position near the middle of a surfacelayer (center side position separated by about ¼ of a wire diameter fromthe surface layer side) on a line corresponding to a wire diameterdirection (direction perpendicular to a longitudinal direction) in thecross section parallel to the longitudinal direction of the wire rod.The average value (N=5) of the measured values was defined as theVickers hardness (HV) of the wire rod. In a case in which the differencebetween the maximum value and the minimum value of the measured valueswas 10 or more, the number of measurements was further increased, andthe average value (N=10) was defined as the Vickers hardness (HV) of thewire rod. The Vickers hardness (HV) was preferably greater, and theVickers hardness of 125 or more was considered to be at a pass level inthe present Examples.

TABLE 1 Evaluation of stucture Average value of size Evaluation ofFibriform perpendicular characteristcs Alloy composition Al and Manu-metallo- to longitudinal Tensile Vickers [% by mass] inevitablefacturing graphic directon of Aspect strength hardness Mg Si Fe Scimpurites condition structure crystal grains ratio MPa HV Examples 10.63 0.61 0.21 — Balance A Presence 240 nm >10 490 130 2 0.63 0.61 0.21— Balance B Presence 190 nm >10 530 143 3 0.63 0.61 0.21 — Balance CPresence 150 nm >10 570 153 4 0.63 0.61 0.21 — Balance D Presence 120nm >10 670 180 5 0.63 0.61 0.21 — Balance E Presence 250 nm >10 490 1286 0.63 0.61 0.21 — Balance F Presence 210 nm >10 520 141 7 0.63 0.610.21 — Balance G Presence 170 nm >10 540 148 8 0.63 0.61 0.21 — BalanceH Presence 140 nm >10 620 162 9 0.18 1.95 0.11 — Balance G Presence 130nm >10 620 165 10 0.22 0.22 0.15 — Balance C Presence 180 nm >10 540 14411 0.63 0.61 1.42 — Balance C Presence 130 nm >10 590 151 12 0.91 0.880.15 — Balance D Presence 90 nm >10 680 181 13 1.76 0.31 0.11 — BalanceH Presence 80 nm >10 660 174 Comparative 1 — — — — Balance C Absence 0.8μm    5 150 43 Examples 2 0.17 0.17 0.21 — Balance A Absence 340 nm >10380 103 3 — 0.02 0.03 0.31 Balance C Absence 0.4 μ m >10 58 210 4 1.822.11 0.21 — Balance K — — — — — 5 0.91 0.88 1.62 — Balance K — — — — — 60.63 0.61 0.21 — Balance J — — — — — 7 0.63 0.61 0.21 — Balance IAbsence 0.5 μ m >10 410 114 8 0.70 0.70 0.03 — Balance P Absence 0.5 μm >10 440 119 9 0.51 0.58 0.79 — Balance Q Absence 5 μ m    2 280 85 100.60 0.30 0.05 — Balance R Abscence 0.5 μ m >10 260 75 (Note) Underlinedbold characters in Table show wire rods outside the appropriate range ofthe present invention and wire rods of which evaluation results do notreach the pass level in the present Examples.

From the results of Table 1, it was confirmed that the aluminum alloywire rod according to each of Examples 1 to 13 of the present disclosurehas a specific alloy composition, and the aluminum alloy wire rod has afibriform metallographic structure where crystal grains extend so as tobe aligned in one direction; and in a cross section parallel to the onedirection, a size perpendicular to a longitudinal direction of thecrystal grains is 270 nm or less. FIG. 3 shows the STEM image of thecross section parallel to the wire drawing direction of the aluminumalloy wire rod according to Example 4. The same metallographic structureas that of FIG. 3 was confirmed also in the cross section parallel tothe longitudinal direction of the aluminum alloy wire rod according toeach of Examples 1 to 3 and 5 to 13. It was confirmed that the aluminummetal wire rod according to each of Examples 1 to 13 of the presentdisclosure having such a specific metallographic structure exhibits ahigh strength comparable to that of an iron-based or copper-based metalmaterial (for example, tensile strength: 480 MPa or more, Vickershardness (HV): 125 or more).

On the other hand, it was confirmed that the alloy composition of thealuminum alloy wire rod of each of Comparative Examples 1 to 3 and 7 to10 does not satisfy the appropriate range of the present disclosure, ordoes not have a fibriform metallographic structure where crystal grainsextend so as to be aligned in one direction; and a size perpendicular toa longitudinal direction of the crystal grains is also 500 nm or more.It was confirmed that the aluminum alloy wire rod of each of ComparativeExamples 1 to 3 and 7 to 10 has a remarkably poorer tensile strength andVickers hardness (HV) than those of the aluminum alloy wire rod of eachof Examples 1 to 13 according to the present disclosure.

Since the alloy composition of the wire rod in each of ComparativeExamples 4 and 5 did not satisfy the appropriate range of the presentdisclosure, working cracks were confirmed to occur in wire drawingworking [1]. Since an aging precipitation heat treatment [0] wasperformed before the wire drawing working [1] in Comparative Example 6,working cracks were confirmed to occur during the wire drawing working[1] performed at a high degree of working in order to increase thecrystal grain boundary.

What is claimed is:
 1. An aluminum alloy material comprising an alloycomposition consisting of 0.2 to 1.8% by mass of Mg, 0.2 to 2.0% by massof Si, 0.01 to 1.50% by mass of Fe, with the balance containing Al andinevitable impurities, wherein the aluminum alloy material has afibriform metallographic structure where crystal grains extend so as tobe aligned in one direction; and in a cross section parallel to the onedirection, an average value of a size perpendicular to a longitudinaldirection of the crystal grains is 270 nm or less.
 2. The aluminum alloymaterial according to claim 1, wherein an aspect ratio of the crystalgrains is in excess of
 10. 3. The aluminum alloy material according toclaim 1, wherein the aluminum alloy material has a Vickers hardness (HV)of 125 to
 250. 4. A conductive member comprising the aluminum alloymaterial according to claim
 1. 5. A battery member comprising thealuminum alloy material according to claim
 1. 6. A fastening componentcomprising the aluminum alloy material according to claim
 1. 7. A springcomponent comprising the aluminum alloy material according to claim 1.8. A structural component comprising the aluminum alloy materialaccording to claim 1.